1. Field of the Invention
The present invention relates to a multilayer ceramic capacitor, and a multilayer ceramic capacitor array including a multilayer ceramic capacitor.
2. Description of the Related Art
Generally, a capacitor device includes a body constituted by alternately stacking inner electrode layers and dielectric layers and outer electrodes disposed on the outer surfaces of the body. In a multilayer ceramic capacitor, the dielectric layers are constituted by a ceramic dielectric material.
Generally, the body of a multilayer ceramic capacitor is formed as follows. The body contains a multilayer unit having a substantially rectangular parallelepiped shape and formed by alternately and densely stacking a plurality of conductive layers, which serve as inner electrode layers, and a plurality of ceramic dielectric layers. Outer layer sections constituted by ceramic dielectric layers and outer layer sections constituted by ceramic dielectric layers and a relatively small number of conductive layers disposed within the ceramic dielectric layers cover the multilayer unit.
In the above-described multilayer ceramic capacitor, the occurrence of cracks in the above-described ceramic dielectric layers may be observed. The occurrence of cracks reduces the reliability of a multilayer ceramic capacitor as a product or decreases the yield in a manufacturing process.
An example of a technique for reducing the occurrence of cracks in a multilayer ceramic capacitor is disclosed in Japanese Unexamined Patent Application Publication No. 2012-248581. In this multilayer ceramic capacitor, a pair of outer layer sections constituted by ceramic dielectric layers that sandwich the above-described multilayer unit therebetween in the stacking direction is provided. In this pair of outer layer sections, one outer layer section that includes the principal surface of the multilayer unit to be mounted on a wiring board is thicker than the other outer layer section.
In this multilayer ceramic capacitor, it is possible to reduce the occurrence of cracks caused by an external stress which is applied to the multilayer ceramic capacitor when the wiring board having the multilayer ceramic capacitor mounted thereon is deflected due to an external force.
However, as a result of conducting an extensive study, the present inventors have discovered the following fact concerning the above-described multilayer ceramic capacitor. If the thickness of the above-described other outer layer section is increased or if the thickness of the above-described multilayer unit is increased, cracks occur at the boundary between the multilayer unit and the outer layer section when the body of the multilayer ceramic capacitor is subjected to firing. Unlike the above-described cracks due to an external stress, this type of crack may occur due to an internal stress produced by the difference in the coefficients of thermal shrinkage between the ceramic dielectric layers and the conductive layers when the body of the multilayer ceramic capacitor is subjected to firing.